CTI Products EXB-232 Asynchronous Serial System Extender - Manual (Page 30)

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EXB Module Phone Line Level Setting
Transmit:
If you are using standard STARPLEX modems and terminations, set the transmit
level on the EXB module to -16 dBm (Option A switch position 7 down). The standard TX
attenuator pad in the STARPLEX termination board is 10 dB. This combination provides the
standard -26 dBm level on the 4-wire TX input to the modem itself.
Receive: For optimum performance, the receive level at the 4-wire input to the EXB must
be between -26 dBm and -16 dBm, with a -20 to -16 dBm level preferred. Using STARPLEX
modems that have been set up for standard levels, you will need a 13 dB Receive attenuator pad
in the termination card.
Warning:
Do not let the receive level into the EXB module exceed -16 dBm.
Receive levels higher than -16 dBm will result in improper operation.
The transmit and receive signal levels can be measured on the backplane of the STARPLEX
system, where the EXB-TELCO module’s 4-wire lines connect to the STARPLEX termination
card’s transmit and receive lines. Refer to Appendix A for a pinout of the EXB-TELCO
module’s 4-wire interface (on the line connector).
EXB Module Switch Settings
The EXB-TELCO modules are configured as follows:
Option A Switch Originate EXB Module Answer EXB Module
1 Down Originate Up Answer
2 Down Leased Line Down Leased Line
3 Up Reserved Up Reserved
4 Up Reserved Up Reserved
5 Up Reserved Up Reserved
6 Down EXB #1 (Originate) Up EXB #2 (Answer)
7 Down -16 dBm TX Level Down -16 dBm TX Level
8 Down 4-Wire Mode Down 4-Wire Mode
STARPLEX Termination Card Jumpering
Set the Transmit and Receive attenuator pads on the STARPLEX termination cards to the loss
shown above. Make sure that the proper jumpers are installed in the termination cards to include
the pads in the signal path and select the resistors for the proper attenuation. The termination
card’s user manual includes a list of attenuation values and the resistor values used to reach the
attenuation.